Fluid-operated motor



Filed July 1, 1941 y T. .F.l s'rAcY 2,454,893

FLUID QPBRATBD KOTOR 2 Sheds-Shoot l IIIL ; i. yINVENTOR AT'roRNEY Nav. 30, 1948. 1-. F. STAcY 2,454,893

y FLUID OPERATBD IIQTOR Filed July l, 1941 2 Shoots-Shut 2 REMI/vn? 46 @gf ffm.,

ATTORNEYS Patented Nov. 30,1948

FLUID-OPERATED MOTOR Thomas F. Stacy, Piqua, Ohio, asslgnor to The glileinch Oil Mill Machinery Company, Piqua,

ApplicationJuly l, 1941, Serial No. 400,607

This invention relates to iluid operated motors such as hydraulic presses, and more particularly to-the mechanism for controlling the oscillations of a ram or working member. It is also in the nature of an improvement on my priorI co-pending application Serial No. 204,375 illed April 26,

1938, now Patent No. 2,335,809, issued November 30, 1943.

An object of the invention is to provide improved controlling means for a iluid operated motor, which will be free of objectionable shock to the system due to the sudden release oi' high pressures in the maincylinder at the time of reversal, with which the full delivery capacity of the pump may be -utilized throughout the normal operations of the motor, but with which the pump will automatically set itself to no-delivery4 condition in the event of failure of the mechanism to reverse the movement of the ram according to a selected control, with which the time cycle oi operation of the motor will be relatively small, with which inching of the ram or platen during preliminary setting up of dies is simplified and better and more sensitive control of the platen movments made possible during inching, and which will be relatively simple, dependable, trouble-free, compact, rapid and inexpensive.

Other objects and advantages will be apparent from the following description of several embodiments of the invention, and the novel features y will be particularly pointed out hereinafter inl connection with the appended claims.

In the accompanying drawings;

Fig. 1 is a. schematic diagram of portions of a f uid actuated motor having a controlling system therefor constructed in accordance with this invention and illustrating one embodiment thereof: Fig. 2 is a schematic diagram showing a modiilcation necessary or desirable when the platen moves horizontally instead of vertically;

Fig. 3 is a similar schematic diagram of the motor with further improvements in the control system shown in Fig. l, and representing a modification or another embodiment thereof; and

Fig. 4 is a schematic diagram of the same motor with a further modification in the control thereof.

In the embodiment off the invention illustrated in Fig. 1, the hydraulic motor is shown as of a type having a ram I carrying a piston 2 operating in a. head 3, the head having a main cylinder 4 at one end and a pull-back, retraction or return 24 Claims. (Cl. 60-52) motors..4 The activity of the ram I is controlled by a main valve l, which is generally the same as the -main control valve of my prior co-pending application above identified. It includes a casing having therein a valve chamber 2 provided with an inlet port 9, and an outlet port AIl connected by a pipe Il to the main cylinder I. The chamber 8 is also provided with an outlet port I2 which is connected by-a pipe I3 toI the retraction or return chamber B. Within the chamber 2 is a reciprocating valve I4 having spaced lands I5 and I8.

chamber: 2l is a chamber 22 which is separated from the chamber 2| by a partition 23. In the chamber 22 is a piston 24 which has a. stem slid# ably guided in an opening in the partition 28, so as to extend into the chamber 2i and into abutting engagement with the adjacent end of the valve element Il when the head of the piston 2li engages with the partition 28 to limit its movement, and the ,valve element IG is in the position shown in full lines in Fig. 1. A spring 25 disposed in one end of the chamber 2 acts against the land IB to urge it in a direction toward the piston 24.

The piston 24 has a stem extending outwardly of its housing where it terminates in a collar or head 2b, and a compression spring 21 surrounding the stem acts between the head 2B and the housing of chamber 22 so as to normally retract the piston Misuillciently to enable movement of the valve element I6 downwardly in Fig. l,`that is. into aposition in which the land I5 is between the ports 9 and I0 and the land I6 uncovers the opposite face of the piston 2. The ram I at its lower end includes a platen -6 which performs the usual function in hydraulic presses or similar port I2, at which time the ports 9 and I2 are connected through the chamber '8. When the valve element Il is moved upwardly in Fig. 1 against the action of spring 25, the land. I5 is carried upwardly beyond the port I0 but below port 29, which thus connects the ports 8 and Ill through the chamber 0, and the port- I2 opens below the land I6. A port 28 at the lower end of chamber 8 thus communicates with port I2 when land I8 moves upwardly beyond port I2, but is disconnected from port I2 when land I8 is in the intermediate position shown by full lines in Fig. 1, or below that position. The chamber 8 is also provided near its opposite end with a port 22.

Vwhich;whenfthe valveelement I4 is in its intermediale position shown in full lines in Fig, 1, is

in communication .with

edge of land I5. When land'I5 moves upwardly. it cuts oi! communication between ports I and 25.

The chamberv22 is connected by a pipe 3l tof vits elevated position in Fig. 1, the lands 35 and 31 connect the pipe 3D to the pipe 32 leading to the pipe i3 and the return chamber 5. When the valve element 35 is in its other end or lower position, the lands 3B and 3.1 connect the pipe 3l! to the pipe 33 leading to the pipe II and main cylinder 4, and interrupt the connection to the pipe 32 leading to the return chamber 5. A spring 38' in the valve chamber 33 normally urges the valve element 35 downwardly out of the position shown in Vfull lines.

The valve element 35 has a stem that depends a substantial distance and extends slidingly through an opening in platen 5. rlJhe element 35 carries a collar 33 adjustably secured thereon at any desired position therealong, so that when the platen 6 approaches its return limit or position, it will engage the collar 39 and shift the valve element 35 upwardly in Fig. 1, so as to connect the return chamber through pipe I3 with pipe 30 leading to chamber 22, thus placing chamber 22 under theV same fluid pressure as that existing in return chamber 5 .and interrupting the connection from pipe 33 to pipe 3G. If desired, a pilot-operated preflll and check valve 40 may be connected to the main cylinder d by a. pipe 4I and to the reservoir by a pipe 52. The pilot chamber of valve 4B is connected by a pipe 43 to the pipe I3, and piston 30a of that chamber is urged in a retracted direction by spring 40h to release free check valve element 50c.

A suitable source of iluid under pressure is employed for operating the hydraulic motor, and this source may be a variable delivery, constantly running pump 44 which is connected at its intake side by a pipe 45 to a suitable reservoir 46 and at its discharge side by a pipe 81 to one side'of a pressure relief or choke valve 53, the other side of that valve being connected by a pipe 49 to the port 5 of the main valve 1. lThe choke or pressure relief valve 5S is set to operate at a relatively low pressure so as to provide a suitable, relatively small, continuous, minimum pressure at the pump or source of uid, for a purpose which will appear presently. A pilot valve 5G has a valve chamber 5I with a port 52 connected by a pipe 53 to the pipe 41, which provides a. pilot operating iiuid under pressure at all times.

An exhaust or drain port of the pilot valve 50 is connected by a pipe 54 to the reservoir 46, and a pipe 54a also connects the exhaust ports `28 and 29 of the valve 1 to reservoir 45. The pilot valve 50 also has a port connected by a pipe 55 to the port 55a in chamber 2l. The valve element 56 of the pilot 5.0 extends outwardly of the valve housing and terminates in a core 51 which is actuated by a solenoid 59 in one direction against the action of a spring 59. Thus, when apipe 33 to the pipe Il leading tov port. l0 while port III is in communication viritlzi port 5, due to the bevelied 4 the solenoid 58 is cie-energiined, the spring 59 urges the valve element Sii-into the position shown in vfull lines, Fig. 1, in which the pipes 54 and 55 are connectedl together and both are disconnected from the pipe 53. `Whenthis happens,

" the uid in the chamber 2I is free to escape back tothe reservoir through pipes 54 and 55 and the'pilot valve chamber. When the solenoid 58 is energized, it shifts-the valve element 55 against the action of spring 53 in a manner to connect pipes 53 and 55 and'interrupt the connection between the pipes 54 and 55 by shifting a land 55a between the ports leading to those Pipes.

The valve element 55 also extends outwardly at the opposite end and is provided with a notch 50 which moves into alinement with a nose 5I of the latch 52 which is pressed by the spring 63 into latching engagement in the notch 60 when the valve element 56 is moved by the solenoid 53 suillclently to tbring notch 80 into alignment with nose 6I'. This prevents return' oi the valve element 56 when the solenoid is then deenergized. The valve element 56 extends through a housing 54 having a chamber 64a, and in this chamber is a piston 55 sliding on the valve element toward and from the latch 52 through one end of the chamber. An end of piston 55 is movable into a position to engage the latch 62 and cam it out of latching engagement with the valve element 56 when fluid under pressure is ladmitted to the chamber Bea of the housing 64.

. tion from its movement under the action oiiiuid pressure in the housing 5t,

The chamber 54a is connected by a pipe 61 to one side of a pressure relief valve 68, the other side of which is connected by a pipe B9 to the pipe II connecting the valve 'l to the main cylinder 4. When the pressure in the main cylinder f3 and the pipe `II reaches the selected pressure for which the relief valve 68 is set, and which pressure setting may be adjustable as usual in this type of valve, the valve 58 opens and passes fluid under pressure from the pipe II through valve 58 and pipe 51 to chamber 64a., and the pressure therein acts against spring' S6 and forces piston 55 in a direction to engage latch 52 and disengage the latterfrom the notch 50, thereby releasing the valve element 56. The spring 53 then shifts the valve element back into the position in which it disconnects the pipe 53 from pipe 55 and reconnects the pipe 55 to the exhaust pipe 55, which removes pressure from chamber 2i of main valve. The solenoid 58 is energized in any suitable manner, such as from line wires L', I.'2 having a switch lil in series with one of them.

The pump 64 has a pilot cylinder 1i which is connected by a pipe 12 to the pipe S1 so that when the pressure relief valve 68 opens and passes nuid under pressure through pipe 61 to chamber 64a, some of the fluid under pressure entering pipe 61 will also pass through pipe 'l2 to pilot cylinder 1I. A piston 13 in the pilot cylinder 1I acts against a yoke-shifting member 15. against the action of a spring 15 which may be adjusted in stress, so that when pressure in the pilot cylinder 1I is suicient to overcomespring 15, it will shift the yoke of the pump and set they pump for rio-delivery condition, even though the pump continues to rotate. This type of pump is well known and is shown only schematically, and the spring 15 may be set so that it will not operate until after the pressure is manually operable switch 84,

higher than suicient to operate relief valve Il. Thus, if the latch piston 65` sticks and does not release the valve element 59 and thus stop the advance of the ram, the pump will then automatically set itself in no-delivery condition, and will maintain that pressure for which it is set to operate. 'I'hus further operation of the press ram will be stopped. This is a desirable safety factor, and since the pilot cylinder 1I of the pump is not connected to uid under pressure until valve 88 opens to cause a release of valve element 56. there will be no diminution in the rate of the uid delivered by the pump during normal operation of the ram.

It is desirable at times, in presses of this type, to inch the platen along in an advancing direction by small increments of movements when setting up dies and getting the machine ready for operation. Heretofore, this inching commonly has been done by operation of the lever I8 to shift the valve element I4 upwardly in Fig. l, and then releasing it at the end of the desired movement increment. I have provided improved means for inching the platen which is supplemental to or may be used in place of the lever I8, and this will now be described.

The pipe I3 leading from the return cylinder 5 is connected by a pipe 15 to one side of an adjustable throttle valve 11 andthe other side of that valve is connected by a pipe 18 to a simple solenoid-operated valve 19, also connected by a pipe 80 to exhaust or reservoir 4B. The solenoid 8| which operates this valve 19 is connected at one side by a wire 82 to line wireL2 and at its other side by wire 83 to line wire L'. One of these wires, such as the wire 88, has in series therein a so that by operating switch 84, the valve 19 may be opened to bleed operating iluid from return cylinder through pipes I3 and 16, throttle valve 11, pipe 18, valve 19 and pipe 80. The throttle valve 17, which is preferably adjustable, .thus regulates the rate o! escape of iluid from the return chamber 5,whi1 valve 1 remains unchanged.

When the valve element I4 of main valve 1 is in its normal or intermediate position. ln which the platen 6 is held in its elevated position, the pipe I3 is connected through valve 9| to the chamber 22, so that thepressure of fluid in return chamber 5 created by supporting the weight of ram lI and platen 6 will be transmitted through pipe 38 to chamber 22 and piston 24 which holds valve element It in thel intermediate or inactiveposition shown inpFig. 1, in which the escape of iluid from the return cylinder 5 through pipe i3 and valve 1 is prevented by the land I8, and the main cylinder is connected through pipe Il and valve 1 to the reservoir 45. By closing the switch 84, operating fluid is drained from return cylinder 5, and as this is done, the ram I descends as rapidly as uid escapes from cylinder 5, which rateis determined by throttle valve 11. During ber is under no pressure. Hence valve element 4 would be free to move, under urge of spring 25. in a direction to connect the pump to return cylinder 5. and-ifsuch movement oi element. I4 occurred, it would cause a return of the platen and thus interfere with the inching operation, except as such discharge was released through valve 19. To prevent this, the valve element I 4 is provided with a passage transversely therethrough, just above the upper end of the housing of valve 1 when valve element I4 is in its intermediate position, and a removable pin 85 may be temporarily passed through this opening in element I4 so as to engage with the top of housing ot valve-1 and prevent movement of valve element I4 upon decrease of pressure in chamber 22 during this inching of the ram. Of course, when the press is in normal operation, the pin 85 is removed and kept removed until one is ready to inch the ram again.

Referring now tothe embodiment of the invention shown in Fig. 3, the arrangement is generally the same as in Fig. 1 and corresponding parts are given the same reference characters. embodiment, however, a valve 86 is included in the pipe 80 connecting the valve 3| to the cham- 22. This valve 88 has a valve element 81 which is operated by a solenoid 88 into a position in which the valve element connects the section of pipe 80 leading to chamber 22 to a pipe 89 and disconnects it from the section leading to valve 3i. A spring 90 urges the valve element 81 into a position in which the two sections of the pipe 30 are connected with one another and disconc, uid pressure nected from the pipe 89. The pipe 89 is connected to pipe 53 leading to pipe 41` and the pump. so that when the solenoide88 is energized, it will operate valve 81 and connect the pump 44 through pipes 41, 53and 89 to the section of the pipe 30 leading to the main valve chamber 22 and to disconnect the two sections of the pipe 30 from one another. This serves to apply the of pump to chamber 22 so that bleeding of pipe i3 while inchlng the ram will not cause a release of valve element I4 of valve 1. Thus, this valve 86 and pipe 89 serve the same function as pin 85 of Fig. 1, and the pin 85 need not be used with this arrangement.

One side of the solenoid 88 ls connected by a wire 9| to wire 82 and the line wire L', and the other side of solenoid 88 is connected by wire 92 to one side of a switch 93, the other side of the switch being connected to line wire L2. In order to avoid bleeding oi the iluid from the return cylinder 5, through pipe I3 by operation of the valve 19, when the valve 86- is not in a position to connect the source of iluid under pressure to the chamber 22, the switch 84 is connected to this descent of ram I, uid enters main cylinder 4 from the pump which is continuously operating. As soon as the switch 84 is released,`the valve 19 closes andstopsA the escape of iiuid from cylinder 5, and this stops the descent of platen 6.

When liquid is released from pipe I3 in this manner, the pressure thereinwill fall momentarily, and since this pipe is connected to chamber 22 in the main valve 1, it may release the valve element I4 suillciently to cause a return of the ram I to its elevated platen 6 drops sumciently, by escape vof liquid through valve 19, to release valve element 35, the latter connects chamber 22 to cylinder 4 which position. As soon as the;

Y designated as the wire 92 so that the circuit from line wire L2 will be through switch 98 controlling the valve 86, then through switch'84, wire 83, solenoid 8l and wire 82 back to line wire L'. Thus, one must while operating switch 84 to cause an operation of the valve 19 and inching of the ram. Otherwise the system operates as explained in connection with the embodiment of the invention shown in Fig. l.

Referring now to the embodiment of the invention shown in Fig. 4, the system is as explained in Fig. 3, except that a modioation has been made in the main valve 1, the modified valve being 1a and in pilot valve.58. In this form of the invention, the -spring 25 (Fig. 1)

which was used in the embodiment shown in Figs.

land 3 to operate valve element I4, is omitted,

In this and the valve element I4 is urged yieldingly in the same: direction as the spring urges it in Figs. 1 and 3, by a uid actuated device, as will now be explained. The housing of the valve 1a is.provided at the end adjacent the lever I8 with a pilot cylinder 94, and the shank of the valve element I4, which normally extends out of the housing of this valve at that end passes through this cylinder 94 from end to end, and within the cylinder 94 carries a land or head 95 which acts as a piston in cylinder 94. The lower part of cylinder 94 is connected to pipe 54a, and the upper end o said cylinder 94 is connected by a pipe 96 to a port 91 in the pilot valve 50. When the valve element of pilot valve 50 is in its normalposition, shown in full lines in Fig. 4, where it is held by the spring 59, the pipe 53 leading from the pump is in communication through the interior of the valve 50 with port 91 and pipe 96. In this type of valv a second land 56h is spaced from the land 56a so that when this pilot valve is in its normal position, iiuid from the pump will pass to the upper or outer end of pilot cylinder 94 and will exert a. pressure on the head 95 so as to urge the valve element I4 against the piston 2 4 in the same manner that vthe spring 25 urged the same valve element in Fig. 1.

The pressure on the upper or outer face of piston head 95 is preferably less than the pressure on the piston 24, so that the piston 24 will hold valve element I4 in its intermediate position, shown in Fig. 4. When the valve element 56 of valve 50 is operated by energization of solenoid 58 under control of switchll, the land 56h will move into a position between port 91 and the inlet port from pipe 53, and the land 56a will move beyond the port opening into pipe and into a position between the latter port and the port opening into pipe 54 which serves to connect pipe 55 to pipe 53 instead of pipe 54, and to connect pipe 96 to exhaust pipe 54 leading to the reservoir 46. This removes pressure from the piston head 95 on the valve element I4 and causes a. pressure on the lower end of valve element I4 which forces it into the position which causes a normal advance of platen 6, the same as for Fig. 1.

In both embodiments of the: invention as shown in Figs. 3 and 4, the pump 44 is shown schematically as a variable delivery type of pump, and the .pilot cylinder 1I is shown associated therewith schematically, but it will be understood that the pump 44 in Figs. 3 and inmay be identical with the pump 44 of Fig. 1.

In the embodiments of the invention shown in Figs. l, 3 and 4, the ram I is disposed in an upright position, so as to descend by gravity in an advancing direction, and the weight of the ram I with its platen 6 furnishes the motive power for inching the ram by bleeding of the operating iiuid from return cylinder 5.` If the ram is djsposed to operate generally horizontally, then force of gravity is not available to perform this inching, and I have shown in Fig. 2, a manner in which this may be accomplished. In the form of the invention shown in Fig. 2, the ram I is disposed to operate horizontally and I provide an additional small cylinder 98 and an auxiliary ram 99 having a. piston head I00 that reciprocates in this cylinder 98. The ram 99 is also connected to the platen 6 so as to urge it in an advancing direction. The outer end of the'cylinder 98 is connected by a pipe IOI to a two-way valve |02, which alternately connects pipe IIII to a pipe I0! leading to the reservoir 140", and to a pipe |04 which is connected to a suitable source of Y fluid under pressure, such as to the -pipe 41 leading from pump 44.V v Y, Y

In the normal operation of the hydraulic motor, the valve |02 is set to "connect the pipes IOI and |03. and the platenmay be advanced and returned in performing press operation Without any interference or aid from theram 99. The chamber of cylinder v98 behind the piston |00 merely fills and discharges iluid from the reservoir. If now, one desires to inch such a horizontally mov ing ram I, the valve |02 is operated to disconnect the pipe |03 from pipe IOI andy connect the latter .to pipe |04 which applies a small urging iiuid pressure in cylinder 98, that tends to urge the platen 9 in an advancing' direction by approximately the same pressure that would be exerted by gravity on the vertically moving ram I in the other embodiments of the invention. The press may then be inched by any of the mechanisms shown and described in connection with Figs. 1,

' 3 and 4. it being understood that this modification shown in Fig. 2 may be used with the mechanisms shown in Figs. 1, 3 and 4 when the ram I is disposed to move horizontally.

It is believed that the operation of the hydraulic motor under the systems which have been hereinabove explained, will be clear from the description that has been given, but it will be briefly summarized.

Referring rst to Fig. 1, the device is shown as in the normal, inoperative position, in which the platen 6 is elevated and held elevated by the blocking of escape of fluid from the return cylin' der 5 through pipe I3 by reason of the land I6 closing port I2 in the main valve 1. In setting up the work to be performed by the press or motor, such as in mounting dies, it is usually desirable to inchthe platen 6 downwardly and to stop it in the different inched positions, such movements being through small increments. When performing this operation with the mechanism of Fig. 1, the pin is inserted through the valve element I4 to prevent movement of the said element under action of spring 25 upon a, fall of pressure in the chamber 22.

The operator mayperform this inching by rocking the lever I8 clockwise in Fig. 1 sufficiently to elevate the valve element I4 as usual heretofore, but preferably the operator merely closes the switch 84 which energizes solenoid 8l and causes an operation of valve 'I9 to connect pipes' I8 and 80, whereupon fluid escapes from return cylinder 5 through pipes I3 and 16, adjustable throttle valve 11 and pipe 18, valve 19 and pipe 80. The rate of escape as provided for by valve 11 determines the rate of descent of platen 8, and upon releasing switch 84, the latter automatically opens, the electromagnet 8i is de-energized, valve 19 is closed and platen 6 at once stops and remains in that stopped position. At this time, the re- 4turn cylinder 5 is in communication through pipe I3, valve 3l and pipe 30 with chamber 22, until the movement oi platen 6 releases valve rod 35 and thereafter valve 3| places chamber 22 in communication with cylinder 4. Hence any` fallen pressure in chamber 22 during such initial increments of descent of platen 6 will not release valve element I4 ior movement in a direction to cause return of the platen Eto its elevated position until valve 3l is released and operates to connect chamber 22 to cylinder 4.

The platen may be inched throughout any desired range of its possible advancing movement,

attacca ai w i4 against movement into a position in which itl causes a return of the ram i to its elevated position. After the inching operation has beeny concluded, the operator removes pin 85, and the device is ready for normal operation. The operator, to cause advance of the platen, closes switch lli which energizes solenoid 5d and operates valve 50 to connect pipe 59 to pipe 5b, thus admitting iluid under pressure to chamber 2i. This i'orces valve element it against action pi spring 25,

which would be upwardly in Fig. 1, so as to connect the pump through pipes lil and 69 with pipe il leading to main cylinder d, and opening pipe i at port i2 to exhaust, whereupon the ram descends in the usual manner. During such descent, check valve t@ opens to'preil the cylinder il, but when the platen 6 encounters resistance, the check valve iii closes and the Huid from the pump forces the piston head t downwardly.

After the piston 6 has descended a short distance, the valve element t5 is released and it` connects pipe iii through pipe 33 with chamber 22, so that when the pressure in the main cylinder di is suihcient to overcome the pressure relief valve 68, fluid will pass through pipes et, valve t8 and pipe 6l to the unlatch cylinder 6ta. This causes a disengagement of latch 82 from valve element 56, whereupon the spring 59 returns the valve element 56 to full line position in Fig. 1, which disconnects :fluid under pressure fromthe chamber 2 I, vents that chamber and allows operation of valve element it by spring 2E into press reversing position. The piston 2d prevents movement of valve element ii beyond intermediate position and into reversing position, until pressure in main cylinder 6i, which is at this time transmitted to chamber 22, through valve 3i, has fallen sufilcientiy to allow -piston 2d to be overcome by spring 25. b

In the embodiment of the invention shown in Fig. 3, the operation is the same as explained in connection with Fig. 1, except that instead of using pin 85 during an inching operation by bleeding the fluid from the return cylinder, the operator merely closes the switch 93 to cause an operation of valve t6 that connects chamber t2 to pump and disconnects it from valve 3l, and while that switch 93 is held closed he closes switch 8d to operate valve it and bleed operating iiuid from the return cylinder in the same manner as explained in connection with Fig. 1.

The embodiment oi the invention shown in Fig. 4 operates the sameas explained in connection with Fig. 3, except that the pilot valve t@ admits fluid alternately to the opposite ends oi? the valve element ifi so as to alternately urge the valve element `Iii in opposite directions. The fluid admitted to pilot cylinder 9d merely performs the same function as spring 25 in Figs. 1 and 3. l

It will be understood that this modication in valves la and En shown in Fig. 4 may also be included in the forms of the invention shown in Figs. 1 and 2, to replace the spring25. It will l also be understood that various changes in the details and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle motor having a main cylinder, a retraction cylinwhich comprises a source of operating fluid underv pressure, a main control valve having a valve element selectively movable between three positions, in onel of which it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which itconnects said source to said retraction cylinder and releases iiuid from said main cylinder, and a third position intermediate said two positions at which it prevents escape of fluid from said retraction cylinder, releases fluid from said main cylinder and by-passes uid from said lsource, means for yieldingly urging said valve element into said another position, hydraulic means for releasably preventing movement Iof said valve element by said urging means into said another position, iiuid actuated means for moving said valve, element into said one .position to start an advance of said ram element, an auxiliary valve controlling said fluid actuated means and having a control member, means yieldingiy urging said control member into a position in which it makes said iiuid actuated means ineiective on said element, means for shifting said control member into a position in which it causes operation of said uid actuated means, means for latching said control memberin saidxlast named position, and means responsive to an operating condition of said motor when said element is moving under pressure existing in said main cylinder for re-A leasing said control member from said latching means to cause a retraction of said element.

2. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylin der, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under third position intermediate said two positions at which it prevents escape of fluid from said retraction cylinder, releases fluid from said main cylinder and by-passes uid from said source,- means for yieldingly urging said valve element into. said another position, hydraulic means for releasably preventing movement of said valve element by said urging means into said another lposition, uid actuated means for moving said valve element into said one position to start an advance of said ram element, an auxiliary valve controlling said fluid actuated means and having a control member, means yicldingly urgingA said control member into a position in which it makes said fluid actuated means ineiective on said valve element, means for shifting said control member into a position in which it causes operation oi said iiuld actuated means, means for latching said control member in said last named position, a hydraulic device responsive to uid pressure and operable on said latching means and scope of the invention as expressed in the appended claims.

I claim as my invention:

1. Improved operating means for a hydraulic` for releasing said control member, a conduit connected to said hydraulic device and having therein a pressure relief valve for passing fluid to said hydraulic device`when pressure in said conduit exceeds a selected pressure, and means for supplying said conduit with fluid under pressure directly responsive to the iluid pressure in said main cylinder.

3. The combination substantially as set forth in claim 1 in which said responsive means responds to uld pressure in said main Vcylinder as said operating condition, andsaid source of fluid under pressure is a variable delivery pump which automatically sets itself to no delivery condition when pressure in a pilot cylinder thereof reaches a selected pressure, and said pressure responsive means includes a pressure relief valve which remains closed until said selected pressure is reached and then opens, and means for delivering uid under pressure to said pilot cylinder concurrently with delivery or fluid to said releasing means for said control member, whereby in the event of failure of said releasing means to release said control member at the selected pressure for which it is set to release, said pump will automatically set itself to no delivery condition.

4. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movable between three positions, in one or' which it connects said source to said main cylinder and releases iluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases fluid from said main cylinder, and a third position intermediate said two positions at which it prevents escape oi fluid from said retraction cylinder, releases uid from said main cylinder and by-passes duid from said source, means ior yieldingly urging said valve element into said another position, hydraulic means for releasably preventing movement of said valve element by said urging means into said another position, fluid actuated means for moving said valve element into said one position to start an advance of said ram element, an auxiliary valve controlling said fluid actuated means and having a control member, 'means yieldingly urging said control member into a position in which it makes said fluid actuated means ineective on said valve element, means for shifting said control member into a position in which it causes operation of said fluid actuated means, means for latching said control member in said last named position, a hydraulic device responsive to duid pressure and operable on said latching means for releasing said control member, a conduit connected to said hydraulic device and having therein a pressure relief valve for passing duid tosaid hydraulic device when pressure in said conduit exceeds a selected pressure, means for supplying-said conduit with fluid under pressure directly responsive to the duid presssure in said main cylinder, said source of iiuid including a variable delivery pump operable to automatically'set itself to no delivery condition whenever pressure in a pilot cylinder thereof reaches a selected pressure, and a connection from said pump pilot cylinder to said conduitbetween said hydraulic device and said pressure relief valve.

5. l'mproved operating means -for a hydraulic motor having a main cylinder, a return cylinder, and a ram advanced by the main cylinder and returned by the return cylinder, and urged yieldingly in the direction of said advance, which comprises a source of operating uid under pressure, means having a single control member for controlling the admission of operating uid from said source alternately to said cylinders and the escape of uid from said cylinders selectively to -cause an advance of said ram, a return of said Vprevent escape of uid from said return cylinder and thus hold said ram against advance by said yielding urge. ram controlled means for holding said control member in travel stopping position when said ram reaches its desired limit of return movement, means by which said control member may be held in its travel stopping position when it is released by said ram controlled means, and means for releasing uid from said return cylinder selectively and separately from said controlling means, and while escape of fluid from said return cylinder is blocked by said controlling means, to allow advance of said ram through selected increments by said yielding urge, and restrict said release of fluid from said return cylinder and thereby control the rate of such advance of said ram in said increments, whereby the ram may be inched without operation of said main control valve.

6. Improved operating means for a hydraulic motor having a main cylinder, a return cylinder,

, and a ram advanced by the main cylinder and returned by the return cylinder, an'd urged yieldingly in the direction of said advance, which comprises a source of operating uid under pressure, means for controlling the admission of operating uid from said source to said cylinders and the escape of uid from said cylinders selectively to cause an advance of said ram, a return of said ram and a stoppage 'of said ram, said means being operable when said ram is stopped thereby to prevent escape of fluid from said return cylinder and release pressure in said main cylinder and thus hold said ram against advance by said yielding urge, ram controlled means for holding said control member in travel stopping position when said ram reaches its desired limit of return movement, means by which said control member may be held in its travel stopping position when it is released by said ram controlled means, and means for releasing uid from said return cylinder selectively and separately rom said controlling means, and while escape of iiuid from said return cylinder is blocked by c said controlling means, to allow advance of said ram through selected increments by said yielding urge,'and restricting said release of uid lfrom said return cylinder to thereby control the rate of such advance of said ram in said increments, whereby the ram may be inched without operation of said main control valve, said fluid releasing means including a throttle-controlled escape passage for regulating the rate of escape of operating duid, and a manually controlled valve for selectively opening and closing said escape passage, whereby the ram may be inched without operation of said main control valve.

7. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by iiuld pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movable between three positions, in one of which it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases fluid from said main cylinder, and a third position intermediate said two positions at which it v f ingly urging said valve element into said another position, hydraulic means Ifor releasably preventing movement of' said valve elementby said urging means into said another position, ram-controlled means including a ram-controlled valve connecting said hydraulic means to said cylinders alternately, said ram controlled valve being operable when said ram is within a selected zone for connecting said hydraulic means to said retraction cylinder, and when out of said zone for connecting said hydraulic means to said main cylinder, and means for releasing fluid from said retraction cylinder separately from said main valve in Vselected increments at will while said main valve element remains in said intermediate position, to inch the ram in an advancing direction and means by which said main valve element may be held in said third position, while said ram is being inched.

8. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movable between three positions, in one of which it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases fluid from said main cylinder, and a third ,position intermediate'said two positions at which it prevents escape of fluid from said retraction cylinder, releases fluid from said main cylinder and by-passes iiuid from said source, means for yieldingly urging said valve element into said another position, hydraulic means for releasably preventing movement of said valve element by said urging means past said third position, ram-controlled means including a ram-controlled valve 14 releasably preventing movement. of said valve ele-l ment by said urging means past said third position, ram-controlled means including a ram-controlled valve connecting said hydraulic means to said cylinders alternately, said ram-controlled valve being operable when said ram is within a selected -zone -ior connecting said hydraulic means to'said retraction cylinder, and when out of said zone for connecting said hydraulic means connecting said hydraulic means to said cylinders alternately, said ram-controlled valve being operable when said ram is within a-selected zone for connecting said hydraulic means to said retraction cylinder, and when out of said zone for connecting said hydraulic means to said main cylinder, means by which said main valve` element may be held in vsaid third position or released, a bleed 'passage for releasing fluid from said retraction cylinder separately from said main valve,

a throttle valve in said passage for regulating the rate of said escape of iiuid, and a manually controlled valve for selectively opening and closing said escape passage to inch the ram in anadvancing direction.

. 9. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in yopposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movable between three positions, in one ofwhich it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases uid from said main cylinder, and a third position intermediate said two positions at which it prevents escape of fluid from said retraction cylinder, releases fluid from said main cylinder and by-passes fluid from said source, means for yieldingly urging said valve element into said another position, hydraulic means for to said main cylinder, means for releasing iluid from said retraction cylinder separately from said' main valve in selected increments at will Whilee said main valve element remains in said intermediate position, to inch the ram in an advancing direction, and means selectively operable to prevent movement of said main valve element from said intermediate position to said another position while inching said ram. y

10. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and aram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movable between three positions, in one of which it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases fluid from said main cylinder, and a third position intermediate said two positions at which it prevents escape of fluid from said retraction cylinder, releases fluid from said main. cylinder and by-passes fluid from said source, means for yieldingly urging said valve element into said another position, hydraulic means for releasablyA preventing movement of said valve element by said urging means pasty said third position, ramcontrolled means including a ram-controlled valve connecting said hydraulic means to said cylinders alternately, said ram-controlled valve being operable when said ram is within a selected zone for connecting said hydraulic means to said retraction cylinder, and when out of said zone for connecting said hydraulic means to said main cylinder, means for 'releasing fluid from said retraction cylinder separately from said main valve in selected increments at will while said main valve element remains in said intermediate pol sition, to inch the ram in an advancing direction, and means for applying fluid pressure from said source to said hydraulic means rand interrupting the connection from said ram-controlled valve to said hydraulic means while inching said ram. v

11. Improved operating means for a hydraulic motor havingv a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, a main control valve having a valve element selectively movableI between three positions, in one of whichr it connects said source to said main cylinder and releases fluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and reed zone for connecting said hydraulic means to said retraction cylinder, and when out of said zone for connecting said hydraulic means to said main cylinder, means for releasing uid from said retraction cylinder, separately from said main.

valve in selected increments at will while said main valve element remains in said intermediate position, to inch the ram in an advancing direction, means included in the connection between said source and said main valve for maintaining a minimum pressure at said source, a selector valve in the connection from said ram-controlled valve to said hydraulic means connected directly to said source and operable to connect said hydraulic means alternately and selectively to said source and to said ram-controlled valve, whereby during inching of said ram, fluidfrom said source may be applied to said hydraulic means to prevent movement of said valve element into said another position.

12. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element -operated in opposite directions by fluid pressures in said cylinders, which comprises a source of ioperating fluid under pressure, means having a single control member for delivering duid ,from said source alternately to said cylinders to control the direction of travel and the activity oi said ram, for releasing duid from either cylinder automatically when fluid is vapplied to the other, and for stopping travel of said ram by releasing fluid pressure in said main cylinder and preventing escape oi fluid from said retraction cylinder, means controlled by said ram element for moving said control member into' travel stopping position and holding it there at the end of a return movement oi said ram element, means for releasing fluid from said retraction cylinder in selected increments while raid main cylinder is free of pressure and said control member is in travel stopping position, to inch said ram in an advancing direction While said iiuid delivering means remains unchanged and means lby which said control member may be held in its travel stopping position during its release by said ram element in an inching operation.

13. Improved operating means for a hydraulic` motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite dlrections by fluid pressures in said cylinders, which comprises a source of operating iiuid under pressure, means having a single control member for deliveringfluid from said source alternately to said cylinders to control the direction of travel and the activity of said ram, for releasing uid from either cylinder automatically when fluid is applied to the other, and for stopping travel of said ram by releasing fluid pressure in said main 16 element in an inching operation, and means for regulating the rate of escape of said fluid from said retraction cylinder by said inching means. 14. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source of operating fluid under pressure, means having a single control member for delivering fluid from said source alternately to said cylinders to control the direction of travel and the activity of said ram, for releasing uid from either cylinder automatically when uid is applied tothe other, and for stopping travel of said ram by. releasing duid pressure in said main cylinder and preventing escape of fluid from said retraction cylinder, means controlled Iby said ram element for moving said control member into travel stopping position and holding it there at the end of a return movement of said ram element, means separate from said rst means for releasing fluid from said retraction cylinder in selected increments while pressure is released from said main cylinder to inch said ram in an advancing direction while said fluid delivering means remains unchanged, means by which said control member may be held in its travel stopping position during its release by said ram element in an inching operation, and means for preventcylinder and preventing escape o fluid from said l retraction cylinder, means controlled by said ram element for moving said control member into travel stopping position and holding it there at the end of a return movement of said ram element, means for releasing fluid from said retrac- 4 tion cylinder in selected increments to inch said ram in an advancing direction while said fluid delivering means remains unchanged andl free of pressure in said main cylinder, means by which said control member may be held in its travel stopping position duringits release by said ram ing operation of said delivering means in a manner to cause retraction of said ram while said inching means is active in inchingsaid ram.

15. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, which comprises a source ooperating fluid under pressure, means including a main valve connected to said source and to said cylinders for delivering iiuid from said source alternately to said cylinders to cause movement of said ram in opposite directions and for releasing fluid from said main cylinder and preventing escape of fluid from said retraction cylinder to stop said ram, means in the connection from said source to said valve for insuring a minimum fluid` pressure at said source, a uid operated system having a pilot control Yvalve connected directly to said source for controlling and operating said main valve and thereby determining the direction of travel of said ram, means for operating said pilot valve in one direction, means yieldingly urging it in the opposite direction, latch means for releasably holding said pilot valve after operation in said one direction against operation by said urging means in the opposite direction, a hydraulically operated device for voperating said latch means and means responsive to the pressure in said main cylinder for passing operating iiuid to said device and causing release of said pilot valve from said latch means when a selected pressure in said main cylinder is reached, said pressure responsive means operating at a higher pressure than that required Ato operate said device, whereby operation of said vthe ram at a selected position yfrom said source said main cylinder and preventing escape of nuid from said retraction cylinder to stop said ram, means in the connection from said source tosaid valve for insuring a minimum iluid pressure at said source, a nuid operated system having a pilot control valve connected directly to said source for controlling and operating said main valve and thereby determining the direction oi' travel of said ram, means for operating said pilot valve in one direction, means yieldingly urging it in the opposite direction, latch means i'or releasably holding said pilot valve after operationvin said one direction against operation by said urging means in the opposite direction, means responsive to the pressure in said main cylinder for releasing said pilot valve from said latch means when a selected pressure in said main cylinder is reached, and ram controlled means'for also controlling said main valve and setting it releasably to prevent escape of uid from said retraction cylinder and release iluid fro'msaid main cylinder to stop in its travel. 1'7. Improved operating means for a hydraulic motor having` a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by fluid pressures in said cylinders, operating uid under pressure, means including a main valve connected to' said source and to said cylinders for delivering iluid from said source alternately to said cylinders to cause movement of said ram in opposite directions and for releasing uid from said main cylinder and preventing escape of uid from said retraction cylinder to stop said ram, means in the connection to said valve for insuring a minimum fluid pressure at said source, a iluid operated system having a pilot control valve connected directly to said source for controlling and operating said main valve and thereby determining the direction of travel of said ram, means for operating said pilot valve in one dil cylinder and preventing escape of fluid from said retraction cylinder to stop said ram, means in the connection from said source to said valve for vinsuring a minimum nuid pressure at said source, a fluid operated system having a pilot control valve connected directly to said source for controlling and operating said main valve and thereby determining yieldingly urging it in the opposite direction, latch means for releasably holdwhich comprises a source oi" rection, means yieldingly urging lit in the opposite -1 direction, -latch meansfor releasably holding said pilot valve after-operation in said one direction against operation by said urging means in the opposite direction, means responsive to the pressure in said main cylinder for releasing said pilot valve from said latch means when a selected pressure in said main cylinder is reached, ram-controlled means for also controlling said main valve and setting it releasably to prevent escape of iluid from said retraction cylinder and release fluid from said main cylinder to stop the ram yai: a selected position in itsy return travel. means for releasing iluid from. said retraction cylinder in selected increments at a selected rate, while said main valve remains unchanged, to cause selected yinching of said ram and means by which said main valve may be held in the position in which it releases iluid from the main cylinder and prevents escape of fluid therethrough from said retraction cylinder'while inching the ram.

18. Improved operating means for a hydraulic motor having a main cylinder, a retraction cylinder, and a ram element operated in opposite directions by iluidl pressures in said cylinders, which comprises a source of operating iluid under pressure, means including a main valve connected said source and to said cylinders for delivering iluid from said source alternately to said cylinders to cause movement of said ram in opposite directions and for releasing fluid from said main element selectively movable draulic means and connecting ing said pilot valve after operation in said one direction against operation by said urging means inthe opposite direction, means responsive the pressure in said main cylinder for releasing valve from said latch means when a selected pressure in said main cylinder is reached, ram controlled means for also main valve and setting it releasably to prevent escape ofiiuid from said retraction cylinder release fluid from said main cylinder to stop ram at a selected position in its travel, means for releasing iluid from said retraction cylinder in selected increments at a selected rate, while said main valve remains unchanged, to cause selected inching of said ram, said ram controlled means including a stop and hydraulic means for operat. ing the stop into a position to prevent operation of said valve in a direction to connect said source to said retraction cylinder, and means also connected directly to said source and operable i'or supplying fluid under pressure directly to said hydraulic means to hold said stop in its said valve movement preventing position while said ram is the . being inchedby releasing fluid from said retrac- 19. Improved operating means for a hydraulic motor having a inder, and directions by vfluid pressures n said cylinders, whichcomprises a sourse of operating fluid under pressure, a main control valve having a valve' between three positions, in one of which it connects said source to said main cylinder and releases uid from said retraction cylinder, in another of which it connects said` source to said retraction cylinder and releases fluid from said main cylinder, and a` third position intermediate said two positions at which it prevents escape of iluid from said retraction cylinder, releases iiuid from said main cylinder andfby-passes fluid from said source, means for yieldingly urging said valve element into said another position, hydraulic means for releasably preventing movement of said valve element by said urging means past said third main cylinder, a retraction cylposition, ram-controlled means including a. ram.`

controlled valve connecting said hydraulic means to said cylinders alternately, said ram controlled valve being operable -when said ram is within a selected zone for connecting said hydraulic means to `said retraction cylinder. and when out of said zone for connecting said hydraulic means to said main cylinder, means for releasing fluid from said retraction cylinder separately from said main valve in selected increments at will while said -main valve element remains in said intermediate position, to inch the ram in an advancing direction, valve means in the connection from said ram-controlled vvalve to said hvdraulif` means for alternately applying iluid pressure to said hythe latter to said ram-controlled valve to said hydraulic means for operation of said fluid releasing means in a mancontrolling said and a ram element operated in opposite motor having directions by ram-controlled valve.

' electrical means for operating said iluid releasing ner to release nuid from vid valve means in the connection to said hydraielic means is operated to disconnect the latter irom said ram-controlled valve and apply fluid pressure to said hydraulic means.

20.' Improved operating means for a hydraulic a main cylinder, a retraction cylram element operated in opposite nuid pressures in said cylinders, which comprises a source oi operating nuid under pressure, amain control valve having a valve element selectively movable between three positions, in one ofwhich it connects said source to said main cylinder and releases iluid from said retraction cylinder, in another of which it connects said source to said retraction cylinder and releases iluid from said main cylinder, and a third position intermediate said two positions at which it prevents escape of iluid from said retraction cylinder, releases fluid from said main cylinder and by-passes iluid from said source, means for yieldingly urging said valve element into said another position, hydraulic means for releasably preventing movement of said valve element by said urging means past said third position, ram-controlled means including a ramcontrolled valve connecting said hydraulic means to said cylinders alternately, said ram-controlled valve being operable when said ram is within a selected zone for connecting said hydraulic means to said retraction cylinder, and when out of said inder, and a zone for connecting said hydraulic means to said main cylinder, -means for releasing iiuid from said retraction cylinder, separately from said, main valve, in selected increments at will while said main valve element remains in said intermediate position, to inch the ram in an advancing direction, valve means in the ;'connection from said ram-controlled valve tosaid hydraulic means for alternately applying fluid pressure to said hydraulic means and connecting the latter to said and individually controlled means and said valve means connected to said hydraulic means, said electrical means beingso interconnected that operation oi' ,said uid releasing means is possible only while said valve means is in a position to apply iluid pressure to said hydraulic means. Y

2l. Improvedoperating means for a hydraulic motor of the type'having a working member and an advancing cylinder and a return cylinder for operating said working member back and forth, which comprises a variable delivery pump, a reversing valve. connections between said pump, said valve and said cylinders by which the delivery of iluid lto said cylinders may be reversed to control the direction of travel of said working member, said reversing valve having a valve element movable into diiIerent positions to control the direction of travel of said working member, means for holding said valve element in the Vposition in which it causes an'adv'ance of said working member but voperable to release said element, means for urging said valve element in a direction to cause a reversal oi travel of the working member, means responsive to iluid pressure in the advancing cylinder for causing a release oi said valve element from said holding means when a desired pressure in said advancing cylinder is reached, and having a pressure relief valve opening to pass `fluid under pressure from said advancing cylinder to said releasing means automatically when adesired pressure has been reached, and means responsive tothe pr'essure said retraction cylinder d said ram element causes delivery of uid to said means for a hydraulic a main chamber, a reelement operated in opposite directions by fluid pressure differentials d in said chambers, which comprises means for delivering operating fluid under pressure alternately to'said chambers to cause movements of said ram element in opposite directions and for closing said retraction chamber to stop an advance of said ram element, and including a control member yieldingly urged into a position to cause a retraction of said ram element, ram controlled means for causing movement oi said control member out of a position in which it retraction chamber to cause a retraction of said ram, at the end of a return movement of the ram and for releasing it in an initial zone of advance of said ram, a selectively operated, valve-controlled connection to said retraction chamber to selectively, and at will, release uid therefrom irrespective oi the position of said control member, and a device by which said control member may be held against movement` into said position in which it causes a retraction of said ram for any desired extent of advance movement of said ram during release of iluid from said retraction chamber.

23. Improved operating means for a hydraulic motor of the type having a main chamber, a retraction chamber, and a. ram element operated in opposite directions by ilud pressure differentials in said chambers, which comprises means for delivering operating iluid under pressure alternately to said chambers to cause movements of in `opposite directions and for closing said retraction chamber to Astop an advance of said ram element, and including a control member yleldingly urged into a position to cause a retraction of said ram element, ramcontrolled means for causing movement of said control member out of a position in which it causes delivery of fluid to said retraction chamber to cause a retraction of said ram, at the end of a return movement of the ram and for releasing it in an initial zone of advance of said ram, a selectively operated, valve-controlled connection to said retraction chamber to selectively, and at will,'release duid therefrom irrespective of the position of said control member, a device by which said control member may be held against movement into said position in which it causes a retraction of said ram for any desired extent of advance movement of said ram during release of iluid from said retraction chamber, and a common control for both said device and said valvecontrolled connection,whereby when said valvecontrolled connection is opened to release uid from said retraction chamber, said holding device will be concurrently rendered effective to pre.

- `ling the direction of movement of said member,

said controlling means having a uid actuated element eective when operated for causing retraction of said member, and connected to said advancing chamber for actuation by the pressure in said, advancing chamber, a pressure relief vvalve in said connection from said element to said ad- Cil vancing chamber and passing uid therethrough towards said element only in excess of a selected pressure on the attainment of which a retraction of said member is desired, and a connection from said element to said fluid responsive means at the discharge side of said pressure relief valve for delivering part of any fluid passed by the pressure relief valve to said uid responsive means to cause a decrease 'in the rate of delivery of uid by the pump after the pressure relief valve opens until the pressure in the advancing chamber has fallen to a selected extent.

THOMAS F. STACY.

29 i .REFERENCES errno The following references are of record in the le of this patent:

UNITED STATES PATENTS Date ,Number Name 1,613,563 Grattan Jan, 4, 1927 1,847,889 Osborne Mar. 1, 1932 1,897,386 Ferris Feb. 14, 1933 1,959,786 Hodgkinson.. May 22, 1934 1,970,998 Ferris Aug. 21, 1934 1,990,052 Sosa Feb; 5, 1935 2,029,708 Douglas Feb. 4, 1936 2,063,122 Richardson Dec. 8. 1936 2,065,219 Ferris Dec. 22, 1936 2,072,488 Stacy Mar. 2, 1937 2,190,939 Ernst Feb. 20, 1940 2,238,060 Kendrick Apr. 15, 1941 2,276,016 Brantly Mar. 10, 1942 2,318,852 Griffith May 11, 1943 2,335,809 Stacy Nov. 30, 1943 2,367,241 Stacy Jan. 16, 1945 Stacy y Apr. 22, 1947 

